The present invention pertains to a phase-shifter. It can be applied especially to an electronic scanning antenna. The invention can also be applied in particular to low-cost electronic scanning antennas used in radars, for example for the management of air traffic in airports, as well as in telecommunications, for example civilian telecommunications.
Passive electronic scanning antennas use phase-shifters for the to mobility of their beam. These phase-shifters can act directly on the radiated wave constituting what is known as a microwave lens. These phase-shifters can also act within an energy distribution device. The amplification of the wave to be transmitted is centralized and then the wave thus amplified is distributed towards the phase-shifters. There are single-plane electronic scanning antennas and two-plane electronic scanning antennas. A single-plane scanning antenna has a linear array of radiating sources each serially connected with a phase-shifter. The direction of the beam is then electronically controlled along a single plane, comprising radiating sources and a direction of radiation. To point a beam in a given direction xcex8, each phase-shifter is controlled so as to create a wave plane perpendicular to the direction of radiation xcex8. To obtain two-plane scanning, the linear array of radiating sources must be extended in a second direction.
Phase-shifters are elementary components that generally associate heterogeneous technologies to obtain microwave and control functions. The microwave functions are carried out especially by waveguides or ceramic substrates. The control functions are carried out especially by logic circuits and power circuits. These different functions are dissociated and require interconnections. The control of a group of phase-shifters also requires interconnections. This results in high costs for making these phase-shifters and therefore for making the electronic scanning antennas that comprise them. This is especially so because the number of phase-shifters is great.
An aim of the invention especially is to enable the making of a low-cost electronic scanning antenna. To this end, an object of the invention is a microwave phase-shifter comprising at least one 3 dB coupler in waveguide form and one pair of phase-shifter cells. The incident wave E enters a first input of the coupler and gets divided into two waves E1, E2, each of these two waves getting reflected on one elementary cell with identical phases and getting recombined into a resultant phase-shifted wave coming out by the output of the coupler juxtaposed with the first input.
Advantageously, to obtain an even more compact and economical phase-shifter, an elementary phase-shifter cell comprises a phase-shifting circuit and a conductive plane positioned substantially in parallel to the phase-shifting circuit, the phase-shifting circuit comprising at least two half phase-shifters, the incident waves E1, E2 being linearly polarized along a first given direction Oy. A half-phase-shifter comprises at least one dielectric support, at least two electrically conductive wires substantially parallel to the given direction Oy, positioned on the support and each bearing at least one semiconductor element with two states D1, D2, each wire being connected to control conductors of the semiconductor elements, these conductors being substantially normal to the wires, and two conductive zones positioned towards the periphery of the cell, substantially parallel to the control conductors. The control conductors are at least three in number in each half-phase-shifter and are electrically insulated from one half-phase-shifter to another, to control the state of all the semiconductor elements independently of one another. The geometrical and electrical characteristics of the half-phase-shifters are such that each of the states of the semiconductor elements has a corresponding given value of phase shift (dxcfx861, . . . , (dxcfx868) of the electromagnetic wave which is reflected by the cell, the state of the semiconductor elements being controlled by an electronic circuit.
The dielectric support may advantageously bear the electronic control circuit of the semiconductors and their interconnections, these semiconductors being for example diodes.
An object of the invention is also an electronic scanning microwave antenna comprising phase-shifters as defined here above.
Advantageously, the phase-shifters are distributed into at least one block, one block comprising a set of pairs of phase-shifter cells made on one and the same part and a set of couplers forming a single part. This arrangement provides, in particular, for testing the phase-shifters in batches. Any malfunctioning phase-shifter block can easily be replaced by another. The test and maintenance of the antenna are thus in particular simplified and their reliability is increased.